1. Field of the Invention
The present invention relates to an evaluation method and an evaluation system of free halogen concentration.
2. Prior Art
The following means has been suggested in order to evaluate free halogen concentration (exhibiting a sterilizing effect) in various liquids.
A catalyst is placed in a flow path of a sample liquid for evaluation and the liquid is allowed to pass through it so that free halogen contained therein is decomposed. Further, a reference electrode is dipped and placed at a position at the downstream of the catalyst in the flow path. On the other hand, a potential-measuring electrode is dipped and placed at a position at the upstream of the catalyst in the flow path. Thus, the corresponding free halogen concentration is evaluated from the electric potential difference between the reference electrode and the potential-measuring electrode.
However, since, upon measurement, the sample liquid continues to pass through the catalyst, the activity of the catalyst is lowered with time. For this reason, conventional problems are that the consumed catalyst has to be exchanged by a new one in a short period and a recycling process has to be applied to the consumed catalyst by a heat treatment or other processes.
Therefore, it is an object of the present invention to provide an evaluation method and an evaluation system of free halogen concentration which eliminate the necessity of early exchanging or recycling of the catalyst, as compared with the conventional method and system.
In order to solve the above-mentioned problems, the present invention has the following technical means.
The evaluation method of free halogen concentration of the present invention is characterized in that: a main flow path of a sample liquid for evaluation and a sub-region which communicates with the main flow path are formed; a potential-measuring electrode is installed in the main path, while a reference electrode is installed in the sub-region at a position where free halogen of the sample liquid has been decomposed; free halogen in the sample liquid is decomposed by a free-halogen decomposing substance in the sub-region; and the free halogen concentration is evaluated from the electric potential difference between the reference electrode and the potential-measuring electrode. The sub-region can be described as a sub-flow path.
Moreover, the evaluation system of free halogen concentration of the present invention is characterized in that: with respect to the main flow path of the sample liquid and the sub-region which communicates with the main flow path, there are provided a potential-measuring electrode that is to be installed in the main flow path, a free-halogen decomposing substance for decomposing free halogen in the sample liquid in the sub-region and a reference electrode that is to be installed in the sub-region at a position where the free halogen in the sample liquid has been decomposed, whereby the free halogen concentration is evaluated from the difference in electric potential between the reference electrode and the potential-measuring electrode.
In the present invention, with respect to the main flow path of a sample liquid for evaluation and the sub-region which communicates with the main flow path, the potential-measuring electrode is installed in the main flow path and the reference electrode is installed in the sub-region at a position where the free halogen in the sample liquid has been decomposed.
Thus, upon measurement, the free halogen in the sample liquid is decomposed by the free-halogen decomposing substance in the sub-region, and the free halogen concentration is evaluated from the electric potential difference between the potential-measuring electrode and the reference electrode that is installed in the sub-region at the position where the free halogen in the sample liquid has been decomposed.
In this case, the free halogen in the sample liquid is allowed to be decomposed in the sub-region by the free-halogen decomposing substance in such a manner that the sample liquid is not allowed to pass through the free-halogen decomposing substance with time. That is, in contrast to a conventional system where the catalyst is installed in the flow path of a sample liquid for evaluation, the sample liquid is not allowed to pass through the free-halogen decomposing substance with time; therefore, the activity of the free-halogen decomposing substance is not susceptible to degradation with time.
For the above-mentioned free-halogen decomposing substance, a catalyst may be used; and activated carbon and oxides of nickel, iron, cobalt, titanium, manganese, etc. can be used as the catalyst. Further, a diaphragm, a salt bridge or a glass filter may also be used as the free-halogen decomposing substance.
An air-releasing means for discharging air and generated gases may be installed in the sub-region. With this arrangement, it is possible to avoid the possibility of the reference electrode being exposed out of the sample liquid by the presence of air and generated gases, and consequently to prevent the measurement of the electric potential difference from being interrupted.